* The challenge can be repeated freely even after you've initially conquered it.
* It spawns twice as many stores as a regular dungeon ...
* ... each of which has high chance of carrying quest or elite items.
* There are also treasures just lying around to help purchase anything.
* Leaving a class challenge alive (even by retiring) allows you to locker anything you carry out for free.
Tinker Bronze is basically an infinite locker with a 1-3 minute lag time. Given everything that, uh, was discussed during the beta I am genuinely curious to know if this is an intended consequence or not.